Ultrahigh-Pressure Metamorphic Rocks In The Dabie-Sulu Orogenic Belt: Compositional Inheritance And Metamorphic Modification

The Dabie-Sulu orogenic belt in east-central China contains one of the largest ultrahigh-pressure ( UHP) metamorphic terranes in the world. The UHP eclogites are associated with gneiss, peridotite and marble. But all these rocks underwent in situ UHP metamorphism during the continental collision in the Triassic. Although fluid action is not significant during cold subduction, it becomes prominent during hot exhumation of UHP slices. Whereas the composition of UHP metamorphic rocks is primarily inherited from their protoliths, they were locally modified by partial melting to varying extents. The partial melting of UHP rocks is highly heterogeneous along the collisional orogen, and achieves a maximum during rifting orogeny at the post-collisional stage. This paper outlines the petrographical features and geochemical compositions of UHP metamorphic rocks, and presents an overview of collisional modification and post-collisional reworking of the subducted continental crust. Further discussions are devoted to continental subduction tectonics, as well as to subduction style, subduction polarity and exhumation mechanism. The results also provide insights into the initiation of continental rifting in a Wilson cycle. Consequently, studies of the Dabie-Sulu orogenic belt have contributed greatly to our understanding of tectonic processes, fluid regime and chemical geodynamics in continental subduction zones.